Heat treat furnace Hoskins

I acquired a Hoskins heat treat furnace Type-FD 2020. It came with a very old Foxboro pyrometer. The furnace is 220v it does not give a temperature rating. The pyrometer goes to 2000 deg. F. I'd like to find out if the furnace is rated for 2000 F. as well. Any one out there ever use one of these old timers and have any idea on the rating? It looks like it could handle some pretty high temp., but I would like to know for sure. I did a search on the net and didn't get anything useful.

Try National Element. http://www.nationalelement.com/lab.cfm Their site says that they purchased Hoskins in 1991 who had been making furnaces since the 20s.

If they cannot help, I would judge the max temperature by the thickness and type of fire brick or insulating block. I'm no expert but did recently build a furnace from scratch using components that were excess to a nearby lab furnace mfg facility. I used insulating components rated for 2300 degrees which I understand is at the high end of temp for heating with typical resistance heating elements.

If you have 3" or more of insulating thickness, you are likely safe at 2000 degrees. Try a test heat and check that the controller, electrics and case don't get too hot and you should be fine.

Jim

Hey, Not to resurrect a dead thread, but did you ever get an answer about your Hoskins Furnace? I was just gifted a 110V FD2020 and want to know what it is capable of. This is the only place on the internet that this model is mentioned, so any help would be much appreciated!

if you burn out the elements trying to get it past 2000F then buy kanthal A-1 or similar nichrome wire and go for a larger gauge and wind them tighter.
this will increase the surface area of the heating element and you should easily be able to get another 200-300F from it.

approaching 2400F is more difficult because you have far less margin to go on and the elements become more sensitive to the atmosphere.

if you see evidence the nichrome is melting into the firebrick then you should be able to figure out your limits from visual inspection of how much hotter the nichrome is vs the rest of the furnace.

in theory you should be able to melt cast iron in a mullite crucible in an electric kanthal a-1 furnace. but you have very little margin to do it. whether or not the firebrick holds up to 100 cycles or more of those temperatures is a different matter. relatively cheap firebrick is used in cone 10 kilns every day and those get to 2400F with A1 wire. but they have a lot of wire in them. the slightly cheaper k-20 brick might survive 2400f temps but not nearly as long.

i wonder if the cost difference between k-20 brick and k-23 brick is simply the energy and time needed to fire them at a higher temperature. (i assume it costs nothing to source the different mixtures of silicon, magnesium, aluminum oxides)